Page 51 - Grapevine March-April 2020

Around The Vineyard

used for the detection as well accreditation of test- Generally, the microbe(s) with the most com-
ing laboratories should be adopted by the grape- petitive growth capacity will overshadow slow
vine industry microbes that grow slower, making the diagnosis
difficult or even sometimes impossible. In some
Different Testing Scenarios cases, the diagnosis will be biased and a laboratory
may not be able to report the disease causal agent
In an ideal world, the nursery or grower is inter- unless sophisticated molecular methods are used
ested in learning that their propagation and plant- (see NGS/HTS section). However, in the case of
ing material is free of important pathogens. But the diagnosis of a declining vine in the vineyard or
unfortunately, many times, the grower may suspect nursery, the identification of the fungal family (i.e.,
disease in the vineyard due to specific symptoms. Diatripaceae species are associated with cankers)
A knowledgeable plant pathologist will be able to or bacterial genus (Agrobacterium species causes
help on statistical sampling as well as what type of crown gall) may be sufficient to decipher the cause
laboratory is best suited for each case. Regardless of the problem. Phytoplasmas (a special type of
of the purpose for testing, below I will describe the bacteria that lack cell walls) and viruses cannot be
most common methods available for the detection cultured and their identification must be carried
of important bacterial, fungal, and viral infecting out using molecular and serological methods.
pathogens.
ELISA, PCR, and RT-PCR
Microbiological Culture
ELISA is the abbreviation for “enzyme-linked
Fungal and bacterial pathogens can be cultured immuno-sorbent assay, and consists of sticking the
and isolated in specialized media. However, virus coat protein on a plastic test plate that was
microorganisms may compete among each other. coated with specific antibodies. The detection can

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